I would like to backup my custom dictionary. It used to be easy to find at C:\Program Files\PCTEX\PCTEXV6\CUSTOM.DIC, but now I cannot locate it. I'm running Vista, and the Dec. 3, 2007 beta.

In the Dec 3, 2007 and later beta releases, user-specific files reside in the "Roaming" folder under Vista. For example, on the Vista machine here they are in the folder
C:\users\username\AppData\Roaming\PCTeX

On XP and Win2K they are in
C:\Documents and Settings\username\Application Data\PCTeX